Battery charging

[allcart]

I have a few 12v 7ah batteries but no charger. I have a 13.8v bench power supply that i power my setup with.

I would like to keep my spare batteries charged for occasional use.

Q. Can i use the bench supply to charge the batteries, or will i have to go and get a dedicated charger.

[ChrisLX200]

Well the bench supply will charge the battery all right but unfortunately it won't realise when the battery is fully charged and so it won't stop trying to pump more current into it.  You need a dedicated charger that will charge the battery then revert to a trickle charge to keep it topped up. Something like an Optimate IV is good, it will monitor the battery condition as well and if the need arises will automatically run a de-sulphate routine.

ChrisH

[Tinker1947]

I think the amps need regulating to charge a lead acid battery, without this something nasty could happen.....Somebody will explain in more detail i'm sure.....

[Chris Rowland]

Set the bench power supply to 13.8V and the current limit to 0.7A and charge.  That's very similar to the float charger that's used with these batteries in emergency lighting and burglar alarms.  The current taken by the battery should drop to something pretty low after a while - 20 to 40mA.   It isn't the fastest way to charge but a whole lot better than letting the batteries go flat.

Chris

[Mr TamiyaCowboy]

Dedicated charger, costs very little when compared to the full price of a new battery. 

charging : 

Lead acid should NOT be charged more than 14.7v, and to be safe have it shut down at around 14.4 volts

lead acid battery should not be DISCHARGE to less than 12.6v. current varys but no crazy 4amp charge cycle

slow and easy is best for lead acid, it give time for the electrons to get absorbed. 

dedicated chargers, these are clever parts of kit, once programed they start to work.

they feed a gentle voltage to the battery, this in turn raises as the amps are pumped in.

as the battery starts to reach capacity, the charger will start to DROP the current. 
So say your charging at 3 amps , as the battery reaches full, and charger shows, you will notice the charger

start to ramp down the current. once charged it cuts current and voltage.

Those cheap chargers you get with batterys in a little plastic brick. the 15+v @500mah 

yeah those things, well its just a 240v to 12v transformer, with a diode and maybe possible a regulator.

all it does is pumps 15v in at 0.5amp no brains nothing, its just keeps feeding juice all the time.

Very crude, no safety cutoff, no overvoltage protection no over current regulation, and we plug in and leave these things for a couple days

charging the battery, its not a good idea if you think about what happens to a battery when it fails .

Do Not use them , use a decent car batetry charger with regulation and cuttoffs built in.

as said you really need to be safe, a lead acid battery can be a nasty piece of kit.

overcharging produces highly flamable gasses , at the same time you could find you have BOILED off all the electrolite

and your battery now resembles a balloon. 

be safe and be smart use a dedicated charger and charge OUTSIDE in a very well vented area away from human and/or animal

Carbattrys and likes need the vent plugs removed, SLA are vented but should NOT be opened up and again charged slowly.